Method of producing one-piece channel shaped piston ring

ABSTRACT

This disclosure provides a novel method of producing a channel shaped piston ring in that a plurality of relatively wide lateral slits are formed by punching together with the oil windows to save time and cost and also to avoid an &#39;&#39;&#39;&#39;end effect&#39;&#39;&#39;&#39; during the electrolytic Cr or Co-W plating treatment of the edge of the ring. The method is carried out by punching a sheet tape to produce the plurality of slits and windows, bending the punched tape into a channel having a C-shaped cross section, curling the C-shaped channel into a ring of larger diameter than the final piston ring, and heat treating the ring after inserting it into a hollow cylinder having an inner diameter slightly smaller than the initial diameter of the curled article. The method is further characterized in that the Cr or Co-W plating of the edges of the ring is carried out either before or after the heat treatment.

United States. Patent 51 3,683,477 Sugahara V 51 Aug. 15, 1972 [5METHOD-OF PRODUCING ONE-PIECE 3,606,359 9/ 1971 McCormick ..277/224CHANNEL SHAPED PISTON RING 72 lnventor: Eisuke Sugahara, c/oKohdanjutaku g g ggl g ggi 1 52 abanedal Klta'ku Attorney-Sughrue,Rothwell, Mion, Zinn & Macpeak [22] Filed: I Oct. 28, 1970 [57] ABSTRACT[21] Appl. No.: 84,705 This disclosure provides a novel method ofproducing a channel shaped piston ring in that a plurality of relativelywide lateral slits are formed by punching [52] together with the oilwindows to save time and cost [51] In CL 3323p 15,06 and also to avoidan end eflect" during the elec- [58] Field of Search ..29/l56.6, 156.63;277/223, g s f zg f 277/224 2; 52% sheet tape to produce the pluralityof slits and windows, bending the punched tape into a channel having aC-shaped cross section, curling the C-shaped chan- [56] Reierences C'tednel into a ring of larger diameter than the final piston UNI D TAPATENTS i'linlg, and hlea:l treating the ring after (ijnserting it lingoa 0 ow cy 1n er aving an inner iameter s1g y 2,565,042 8/ I951 PhlllipS..277/235 A X Smaller than the initial diameter f the curled article2,696,038 l2/ I954 Hunt ..204/25 X The method i further characterized ithat the or C0-W plating of the edges of the ring is carried out all e hft h h It m L 3,539,192 11/1970 Prasse ..277/224 er er e ea rea en3,586,544 6/1971 Geffroy ..29/ 156.6 2 Claims, 7 Drawing Figures r 2 1 ra q .j, x 0 Z METHOD OF PRODUCING ONE-PIECE CHANNEL SHAPED PISTON RINGBACKGROUND OF THE INVENTION 1. Field of the Invention This inventionrelates to an improved one-piece channel shaped piston ring of the typeshown in U.S. Pat. No. 2,932,543, and to a method of producing the same.

2. Description of the Prior Art The known one-piece oil rings orone-piece channel shaped piston rings are produced by punching a firstplurality of same sized oil windows in a thin steel sheet tape atregular intervals along the centerline of steel sheet tape, cutting aplurality of lateral slits from the tape edges to the oil windowalternately for every other window by a grinder, bending longitudinallythe obtained steel sheet tape along two lines parallel to the centerlineof the tape, into a channel shaped article, and forming the obtainedchannel shaped article into a ring of desired diameter.

The aforesaid slit cutting step requires much time and cost, and wrongslits are often cut at undesired portions of the steel sheet tape.Besides, as the slits terminate on a sliding face which is formed on anend of a sidewall of the channel, this causes an end effect while thesliding face is subject to the electrolytic Cr plating. This end effectis very detrimental to the Cr plating treatment, and accordingly the endface having the slits is hardly subjected to the Cr plating. By thesereasons, the conventional channel shaped piston ring does not havefavorable durability.

SUMMARY OF THE INVENTION Therefore, an object of this invention is toprovide a novel slit cutting method with saving in cost and workingtime.

Another object of this invention is to eliminate the end effect when theouter surface of the piston ring, especially the sliding face, issubjected to the electrolytic plating treatment. This invention alsoprovides an improved channel shaped piston ring having Co-Mo platedlayer on the sliding face with favorable durability.

BRIEF DESCRIPTION OF THE DRAWINGS More specified embodiments of thisinvention will be described with reference to accompanied drawings,wherein:

FIG. 1 is a plan view of a steel sheet tape to be formed into theconventional channel shaped piston ring, having a plurality of punchedoil windows and lateral slits therefrom, cut by the grinder,

FIG. 2 shows a lateral cross section of a conventional channel shapedpiston ring,

FIG. 3 is a cross section of a conventional assembly composed of apiston, a cylinder and the channel shaped piston ring insertedtherebetween,

FIG. 4 is a plan view of a steel sheet tape to be formed into thechannel shaped piston ring according to this invention, having aplurality of oil windows and slits which are punched in one step,

FIG. 5 shows a partly broken cross section of the steel article bentfirst to have C shaped cross section and then curled on a drum, and

FIGS. 60 and 6b are cross sections of an oil ring whose outer edges arecoated with Co-W plating layer, according to this invention.

Referring to FIGS. l-3, the conventional channel shaped piston ring andthe method of producing the latter will be first described. The steelsheet tape 1 has a plurality of rectangular oil windows 2 at regularintervals and lateral slits 3, 3' arranged alternately on respectivesides of the tape 1. It is bent longitudinally along lines a-a to formthe channel composed of a pair of side walls 4 and 5 and a bottom plateincluding the oil windows 2. End faces or edges 6 of both said sideplates serve as the sliding faces. This channel shaped article is cutinto the desired length and bent into a ring form. The obtained pistonring is inserted into an oil ring groove G of a piston so that the upperface 4 and the lower face 5 touch the groove walls and the sliding faces6 are brought into contact with a surface of a cylinder c which isengaged by the piston.

Thus, the excess oil stuck to the cylinder surface is scraped by the oilring and drained through the oil windows 2 and oil ducts O in the pistoninto an oil pan, as shown in FIG. 3.

This conventional channel shaped piston ring has aforesaid defects, andtherefore an improved oil ring is produced according to this invention,which is described with reference to FIGS. 4-6. A thin steel sheet tape1 is first punched to form a plurality of oil windows 2 of the same sizearranged at regular intervals and to form also, a plurality ofrelatively wide lateral slits 3, 3' which are provided alternately onboth sides of the tape 1 and connect the oil window 2 with the tapeedge. Then, the punched tape is bent along 2 lines a-a and a-a, bothbeing parallel to the tape centerline X-X, to form a channel having thesymmetrical C shaped cross section.

The obtained channel article is curled to form a ring having a diameterlarger than that of the final oil ring product, and the curled articleis inserted into a hollow cylinder having the inner diameter smallerthan the curling diameter and heat treated therein.

After that, an electrolytic Cr plating is applied to the outer surfaceof the curled article to coat a Cr layer 8' thereon.

According to this method, as the oil windows 2 and the slit 3 arepunched simultaneously in one step, the slit forming working is muchsimplified and the cutting of a wrong slit at an undesired point isfully eliminated. The punched slit is wider as compared with the cutslit to reduce the spring characteristics of the resultant oil ring, butthe width of the slit can be adjusted during the heat treatment torecover the spring characteristics of the oil ring. Besides, the heattreatment is able to relieve the internal stress caused by the punchingto recover the favorable mechanical properties, and the resultant oilring exhibits mechanical stability for long periods of time.

On the other hand, the wider slits inhibit any formation of the endeffect" during the Cr plating treatment, thus forming a favorable Crplated layer on the outer edge surfaces of the oil ring. It is moreadvantageous to effect the brushing plating together with the Crplating.

In another example of producing the oil ring, Co-W plating is applied tothe outer surface of the curled channel shaped article prior to the heattreatment in the cylinder 8. This heat treatment is conducted at 200-500C. to obtain the C-W layer having a hardness of 800-1200 Hv. As thisCo-W plated layer is very smooth, a polishing treatment is not required.This is considered to be dependent on a fact that the uniform electricdepositing property of the Co-W layer is excellent and the end effect ishardly present due to the relatively wide slits.

While this reference to particular embodiments thereof, it will beunderstood that the numerous modifications may be made by those skilledin the art without actually departing from the scope of this invention.

Therefore, the appended claims are intended to cover all such equivalentvariations as coming within the true spirit and scope of the invention.

What is claimed is:

1. A method of producing a one-piece channel shaped piston ringcomprising:

punching a plurality of oil windows of the same size,

arranged at regular intervals along a longitudinal centerline within athin sheet steel tape and simultaneously, a plurality of relatively widelateral slits alternately in every other window on respective sides ofthe tape with each of the oil windows connected to a respective tapeedge,

bending the punched tape along two lines parallel to the tape centerlineto form a channel having a symmetrical C shaped cross section,

curling the channel article into a ring having the diameter slightlylarger than that of the final oil invention has been described with l0ring product,

inserting the curled article into a hollow cylinder having an innerdiameter slightly smaller than the initial diameter of the curledarticle,

heat-treating the curled article therein, and

subjecting the outer edge surfaces of the heat treated article to anelectrolytic Cr plating treatment.

2. A method of producing a one-piece channel shaped piston ringcomprising:

punching a thin steel sheet tape with a plurality of oil windows of thesame size arranged at regular intervals along a longitudinal centerlineof the tape and simultaneously with a plurality of relatively widelateral slits provided alternately for every other window on both sidesof the tape for connecting each of the oil windows to respective tapeedges,

bending the punched tape along two lines in parallel to the longitudinalcenterline of the tape to form a channel having the symmetrical C shapedcross section,

curling the channel article into a ring having a diameter slightlylarger than that of the final oil ring product,

subjecting the outer edge surfaces of the curled article to a Co-Wplating treatment,

inserting the Co-W plated article into a hollow cylinder having theinner diameter slightly smaller than the initial diameter of the Co-Wplated article, and

heat-treating the plated article therein.

UNITED STATES PATENT OFFICE v 'CERTIFICATE OF CORRECTION Patent No. ,477Dated August 15, 1972 Inventor) E'isuke Sugahara It is certified'thaterror appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

T The priority'date was omitted from the patent. It should be:

October 28, 1969 The Assignee's name was ornitt ed'from the patent. Itshould be:.

Nippon Piston Ring o. Ltd,

Signed and sealed this 1st day of May 1973.

(SEAL) Attsst:

EDL'JARD M. FLETCHER, ROBERT GOTTSCHAIK Attssting Officer Commissionerof. Patents uscoMM-Dc scan-P69 U,5. GOVERNMENT PRINTING OFFICE: I9690-366-334 FORM PO-1050(10-69)

2. A method of producing a one-piece channel shaped piston ringcomprising: punching a thin steel sheet tape with a plurality of oilwindows of the same size arranged at regular intervals along alongitudinal centerline of the tape and simultaneously with a pluralityof relatively wide lateral slits provided alternately for every otherwindow on both sides of the tape for connecting each of the oil windowsto respective tape edges, bending the punched tape along two lines inparallel to the longitudinal centerline of the tape to form a channelhaving the symmetrical C shaped cross section, curling the channelarticle into a ring having a diameter slightly larger than that of thefinal oil ring product, subjecting the outer edge surfaces of the curledarticle to a Co-W plating treatment, inserting the Co-W plated articleinto a hollow cylinder having the inner diameter slightly smaller thanthe initial diameter of the Co-W plated article, and heat-treating theplated article therein.